The present invention relates generally to water treatment and, more particularly, to the chemical treatment of swimming pool water. In order to keep swimming pool water clear and free of unwanted biological growth, measured amounts of chlorine are commonly added to the pool water at given intervals. One common method of making chlorine additions is to add chlorine in the form of dry, granular calcium hypochlorite on a daily basis in a measured dose of, for example, 3-4 ounces per 5,000 gallons of contained pool water. In order to make the task of adding chlorine easier for the pool owner, and to extend the life of the chlorine, it is common to add an isocyanurate stabilizer to the pool water to prevent the usual rapid dissipation of chlorine which is caused by ultraviolet light degradation to thus permit less frequent chlorine additions. Chlorine has also been formulated into a slow-acting tablet form, commonly referred to as stabilized concentrated chlorinating tablets, which conveniently allows chlorine additions on a weekly basis. While stabilized chlorinating tablets offer a significant convenience in the maintenance of pool water, they, likewise, possess an inherent shortcoming. Commonly used isocyanurate stabilizers form isocyanuric acid in the pool water, also known as fulminuric acid (2-cyano-2-nitroethanamide) represented by the chemical formula CNCN(NO.sub.2)CONH.sub.2.
It is observed that the isocyanuric acid concentration continues to increase in the pool water as additional isocyanurate stabilizers are added over a period of time. When the isocyanuric acid concentration in the pool water reaches a level of about 100 parts per million (PPM), a so-called "chlorine lock" occurs which renders further chlorine additions as ineffective. This condition is easily detected by way of a known pool water test wherein a conventional isocyanuric reagent turns progressively foggy within prescribed limits.
When such a chlorine lock occurs, it is common practice to drain the saturated pool water and replace it with fresh water. Of course, continued isocyanurate stabilizer additions eventually cause a similar chlorine lock to occur in the replaced water which requires yet another drain and replacement. Needless to say, this conventional practice of correcting the chlorine lock problem due to accumulated isocyanuric acid is not only inconvenient to the pool owner, requiring pool shut down, but also is expensive with respect to the high cost of replacement water which in a typical swimming pool may be on the order of about 30,000 gallons, for example.